The present disclosure relates to an spatial image display apparatus that displays an image in the air.
Japanese Unexamined Patent Application Publication No. 2008-158114 discloses an optical system that uses a plane-symmetric imaging device and forms an image of an object positioned below the underside of the device at a plane-symmetrical position with the top side of the device as a symmetry plane. A plurality of penetrating holes are provided in a matrix formation on a substrate of the plane symmetry imaging device used in the optical system and an optical element that includes two mirror surfaces orthogonal to each other is formed on an inner wall of each hole. When light emitted from the object penetrates the holes, the light is reflected on the two mirror surfaces once, respectively, and then, the reflected light forms an image at a plane-symmetrical position. As a result, the image (real image) is viewed to be levitating above the top surface of the element to an observer.